Though most of our attention these days is focused on the transition to IP video technology, it's important to note that analog CCTV security cameras can still be highly effective for many surveillance applications, especially those on a budget. With traditional CCTV security cameras, the video signal is processed and transmitted in analog format for local viewing from one central monitoring location. But that doesn't mean you can't use analog cameras in an IP-based surveillance environment. Using IP video encoders and other equipment such as digital video recorders and hybrid DVRs makes it possible to leverage your existing analog cameras while migrating into the world of digital surveillance.
What is a CCTV security camera?
In its truest form, a CCTV camera is an analog video camera that transmits signals via coaxial cable to a single central location for monitoring, recording, and video analysis. While the recent trend is a push towards IP network cameras, CCTV cameras are still widely used, and offer a cost-effective answer to many common surveillance scenarios.
CCTV technology has been around since the 1940's, and became a major player in the security industry around 1970. The technology is tried and true, and there are CCTV security camera models for virtually any surveillance application. The two main categories of CCTV cameras are fixed cameras and pan/tilt/zoom models which can rotate horizontally and vertically to cover more area.
Pros and Cons of Analog Surveillance
These days, there's a lot to think about when putting together a video surveillance system. And the first question on most people's minds is “Do I go with traditional analog cameras, or IP network cameras?” There are pros and cons to both choices. Let's focus our attention on analog CCTV surveillance cameras.
Pros of analog CCTV
- Lower initial cost - In most cases, analog cameras cost less up front than IP network cameras.
- Wide-spread compatibility - Mixing and matching camera models and surveillance equipment form different manufacturers is easy with an analog CCTV security camera.
- Lower initial cost - Analog cameras tend to handle low-light situations better than IP cameras on average, though IP camera technology is improving in this regard.
Cons of analog CCTV
- Expensive cabling - For large-scale surveillance applications, analog cameras require complicated cabling schemes that can be quite expensive and also challenging to install.
- Limited features - Many of the advanced features now available with IP cameras (for instance: megapixel resolution, digital zoom, and video analytics), aren't available in analog CCTV models.
Components of a CCTV Video Surveillance System
There's a lot that goes into a typical CCTV video surveillance system. While the cameras get most of the attention in the beginning, you also have other concerns, such as viewing, recording, and archiving the video footage, and the equipment required for carrying out those tasks. Here's a look at the basic components of a typical CCTV system.
Security cameras are the starting point for most CCTV video surveillance systems. There are endless possibilities when choosing CCTV cameras and lenses – everything from fixed models designed for monitoring very specific locations, to day/night cameras, and powerful PTZ domes for patrolling large areas.
In a traditional CCTV security camera setup, operators view footage from a central location on a monitor very much like a TV, but with higher lines of resolution for better picture quality. Monitors can be dedicated (meaning they display video from a single camera), or call-up (meaning operators can access multiple cameras at the same time).
With an analog system, coaxial cable is required for transmitting video footage from the CCTV security cameras. This is one of the drawbacks of analog CCTV video surveillance, as the cable can be expensive and difficult to install, especially for larger camera networks, and those were cameras must be positioned in difficult locations.
Most modern CCTV video surveillance systems incorporate DVRs (digital video recorders) which enable operators to reap some of the benefits of a network-based surveillance setup. DVRs convert the analog footage to digital, which helps to extend storage capacity, makes it much easier to search archived footage, and also allows users to stream video over a network for remote viewing from multiple locations.
CCTV Security Camera Types
Fixed CCTV surveillance cameras
Fixed security cameras point in a single direction, which makes them perfect for monitoring very specific areas of interest. They're also preferred for applications where it's beneficial to install cameras in clearly visible locations. For this reason, fixed CCTV surveillance cameras are quite effective not only for capturing footage of suspicious activity, but also for deterring criminals and vandals from carrying out their acts in the first place. The direction of the camera is set during installation. Many security cameras also accept interchangeable lenses and housings, so you have the flexibility to meet a wide variety of surveillance needs.
PTZ cameras are ideal for wide-area surveillance. They give operators the ability to remotely control pan, tilt, and zoom functions to follow activity and to zoom in for detailed monitoring. This is an area where analog CCTV security cameras fall behind their IP camera counterparts. With IP cameras, the pan/tilt/zoom functions are controlled manually or automatically and delivered over a single network cable, while analog cameras require additional wiring to perform similar functionality.
Measuring CCTV Image Quality
Understanding TVL Resolution
The image detail of an analog CCTV surveillance camera is usually conveyed in a form of measurement called TVL (or TV Lines). Think of the video picture as being composed of active horizontal lines. These lines are delivered to a monitor or recording device in two off-set fields. One field contains even-numbered lines while the other contains odd-numbered lines. The viewer sees a complete picture because the lines are interlaced. Since the picture has a 3x4 aspect ratio, the amount of detail you can measure in 3/4 of the picture's width determines the horizontal TVL resolution. Generally, most standard CCTV cameras offer a TVL resolution of around 380, while high-resolution cameras will deliver something closer to 540 TVL.
Effects of Digital Conversion on Image Quality
Most analog CCTV systems today use a DVR as the recording medium. This allows the analog signals to be digitized for recording and for delivery over the network. While a DVR solution is a cost-effective alternative to IP video, and provides users with valuable benefits such as digital storage and remote accessibility, there are drawbacks. One is a slight drop-off in image quality. Simply put, it's harder to retain image quality in this type of setup because of the various analog-to-digital conversions that take place from the camera to the recorder. Cabling distance also plays a role, as the further the video signals travel, the weaker they become. Still, a DVR-based solution is a very good option for users looking to reap some of the benefits of digital IP surveillance while using lower-cost CCTV security cameras.